1. Field of the Invention
The present invention relates to a laminated heat exchanger having a plurality of heat transfer plates having a multiplicity of thicknesswise through holes and a plurality of spacers, the heat transfer plates and the spacers are laminated alternatingly such that the spacers define a plurality of fluid passages which extend in the direction of lamination across the heat transfer plates, the adjacent fluid passages being separated from each other by the spacer.
2. Description of the Prior Art
As shown in FIGS. 1 and 2, a typical laminated heat exchanger has a plurality of heat transfer plates 2 each having a multiplicity of holes 1 and spacers 5 and 6, the heat transfer plates 2 and the spacers 5, 6 are laminated alternatingly such that the spacers 5, 6 define passages 3 and 4 for different fluids A and B between which the heat is exchanged. The fluid passages 3 and 4 are formed concentrically with each other. The areas Sa and Sb of the passages for the fluids A and B are given by the following equations (1) and (2), respectively. EQU Sa=.pi./4d.sub.1.sup.2 ( 1) EQU Sb=.pi./4(d.sub.3.sup.2 -d.sub.2.sup.2) (2)
In designing the heat exchanger, these passages are determined in accordance with the flow rates of the fluids A and B. On the other hand, the heat transfer performance of the heat transfer plate 2 is largely varied by the radial widths of the fluid passages. Namely, the heat transfer efficiency of the heat transfer plate as a fin is improved as the value d.sub.1 /2 and (d.sub.3 -d.sub.2)/2 in respective equations are made small. For obtaining larger flow rates of the fluids A and B, it is necessary to preserve sufficiently large areas Sa and Sb of the fluid passages. This, however, decrease the fin efficiency to lower the efficiency of the heat exchanger as a whole.
For increasing the area of the flow passages while limiting the width of each passage, it is considered to employ additional spacer or spacers to form additional concentric passages around the circle of the diameter d.sub.4 in FIG. 1, thereby to increase the number of the passages. In such a case, a plurality of passages separated by the spacers are used for each of the fluids A and B, so that there is a fear that each fluid is unevenly distributed to these passages to deteriorate the heat exchanging efficiency. In addition, the headers for each of the fluids A and B has to have a complicated construction to distribute the fluid to a plurality of passages and to collect the same from a plurality of passages.